No, there is no provision (at least as at Emacs 24.5) for additionally continuing to look for and process ancestor .dir-locals.el
files after a nearer one has been located.
However, if it makes sense for your scenario, you can remove your "current directory" file and specify all the variables in the parent .dir-locals.el
file.
Keys which are strings specify sub-directories; and the variables beneath that are set in addition to (or perhaps overriding) the ones in the top-level specifications.
See C-hig (emacs) Directory Variables
, which provides the following example:
((nil . ((indent-tabs-mode . t)
(fill-column . 80)))
(c-mode . ((c-file-style . "BSD")
(subdirs . nil)))
("src/imported"
. ((nil . ((change-log-default-name
. "ChangeLog.local"))))))
This sets ‘indent-tabs-mode’ and ‘fill-column’ for any file in the
directory tree, and the indentation style for any C source file. The
special ‘subdirs’ element is not a variable, but a special keyword which
indicates that the C mode settings are only to be applied in the current
directory, not in any subdirectories. Finally, it specifies a different
‘ChangeLog’ file name for any file in the ‘src/imported’ subdirectory.